1. Field of the Invention
The present invention relates to an apparatus, method, computer program, and recording medium for processing an image for use in an image pickup apparatus, for example. In particular, the present invention relates to a technique that outline enhances input video data in a manner free from image degradation by separating an edge component from a smoothing process result of the input video data with an edge component thereof preserved, and by adjusting a level of the input video data.
2. Description of the Related Art
Video apparatuses for processing a variety of video data enhance an outline in a corresponding image with an outline enhancing circuit to improve image quality.
FIG. 7 is a block diagram of a typical known outline enhancing circuit 1. In the outline enhancing circuit 1, a sharpness component extractor 2, including a high-pass filter for example, extracts and outputs a high-frequency component from input video signal Y1, thereby extracting a component for use in an outline enhancement process. An amplifier 3 amplifies the high-frequency component with a predetermined gain, and outputs the amplified component. An adder 4 adds the output signal from the amplifier 3 to the original video signal Y1, thereby enhancing the outline of a video signal Y2 with the edge component thereof enhanced as shown in FIGS. 8A and 8B.
Japanese Unexamined Patent Application Publication No. 2001-298621 discloses a technique of improving contrast and sharpness. As shown in FIG. 9, in an image processing circuit 6 related to the disclosed technique, a separator 7 limits the bandwidth of a luminance signal Y1 with a non-linear filter, thereby smoothing the luminance signal Y1 with an edge component thereof preserved, and outputting a luminance signal ST1 as shown in FIGS. 10A and 10B. The separator 7 subtracts the smoothed luminance signal ST1 from the luminance signal Y1, thereby extracting a high-frequency component TX1 not containing the edge component as shown in FIG. 10C. The non-linear filter is a two-dimensional ε filter, for example.
An amplifier 8 in the image processing circuit 6 amplifies the high-frequency component TX1 not containing the edge component with a predetermined gain and outputs the amplified high-frequency component TX2. An adder 9 adds the output signal TX2 from the amplifier 8 to the smoothed luminance signal ST1 output from the separator 7, and thus outputs a luminance signal Y3 with an edge component removed therefrom and the high-frequency component enhanced. Since the edge component is not processed at all in this method, enhancement is performed with the occurrence of pre-shooting and over-shooting controlled.
The known outline enhancing circuit of FIG. 7 enhances a high-frequency component other than the edge component, thereby enhancing a noise component. This process makes noise pronounced, leading to image quality degradation.
So-called coring process may be contemplated to remove noise component. If a noise component and a variation in signal level, each having a level higher than a coring level, are superimposed on an edge, etc., these signals cannot be removed. This technique has room for improvement.